The invention concerns a granulating apparatus.
Granulating means are known (DE-AS No. 12 87 045), and are used for example in the processing of sugar massecuite into granules or in the production of feed. In those cases a rotating hollow roll is provided, with which on diametrically opposed parts of the inner wall located approximately in a horizontal plane, two contact pressure rolls are associated, intended to press out the material to be processed, introduced axially into the hollow roll, in the area between the driven hollow roll and the contact pressure rolls through orifices in the hollow roll. A gap is provided between the contact pressure rolls and the inwardly directed circumference of the hollow roll. The higher pressure prevailing in the form of this gap is sufficient to press the material in granulating strands out through the orifices. A blade is applied against the outside circumference of the hollow roll, whereby the granulating strands are cut into suitable lengths.
Granulating devices of this type have the disadvantage that they cannot be used for all masses to be granulated. Relatively low viscosity masses cannot be processed in this manner, as it cannot be prevented that such masses flow out by themselves at least partially through the orifices of the rotating hollow roll. A further disadvantage consists of the fact that the extruded masses cannot be metered other than in a very coarse manner, by means of the scraper blade.
For this reason, in particular for masses tending to drip, different devices with rotating perforated hollow rolls have been provided (DE P No. 29 41 802), wherein the mass to be processed is extruded by a certain pressure through a stationary row of orifices and is deposited in the form of droplets by means of intermittently passing orifices of a perforated hollow cylinder, onto a cooling conveyor under said cylinder. These so-called droplet formers have proved to be highly advantageous in actual practice, but have certain disadvantages in the extrusion of high viscosity masses. It is further not possible with these devices to always produce drops with a certain volume, independently of the mass to be granulated.
Another apparatus is also known (DE-AS No. 12 37 540), wherein a stationary hollow roll equipped on its circumference with axially extending toothed ledges is provided. That roll is open on its frontal sides and protrudes into a container in which the material to be granulated is moving from top to bottom in the form of a bulk material. Inside the stationary toothed hollow roll, a dual arm is supported rotatingly around the axle of said hollow roll. That dual arm is equipped on both ends with a toothed contact pressure roll, with the teeth of the contact pressure rolls corresponding to the toothing of the hollow roll. The hollow roll is perforated in a part of its circumference protruding from the supply container, with holes being provided both in the tooth base of the toothed ledges and in the locations of the toothed ledges protruding farthest radially inside. The material to be granulated in this apparatus exits in the shape of small sausages. The disadvantage of such a layout, in which the revolving contact pressure rolls rotate at a high velocity and may be present in multiples, is that the metering of the material emerging in sausage form is not possible. It is further not possible to granulate the material in the form of droplets and to maintain a constant volume of such droplets. This known design is therefore not suitable for any application wherein granulation is to produce pill shapes and in which the volumetric determination of the volume of individual pills is necessary, as for example in the case of the pharmaceutical industry.
It is, therefore, the object of the invention to design a granulating apparatus of the aforementioned type in a manner such that it is well suited for the processing, in particular, of high viscosity materials and that it makes possible the accurate metering of the granules of the material to be processed.